Torsion Keys will not work for your truck, you will need a lower front strut mount extension (some kits use upper as well). Some of the kits account for magneride and provide sensor relocation brackets, others you will need to have the system recalibrated. check out this thread for a better idea
http://www.gm-trucks.com/forums/topic/168618-leveling-kit-for-2015-sierra-denali-magnetic-ride/page-3